A human body includes biometric information items which make it possible to identify an individual, and some of the biometric information items are used as information for identifying and authenticating the individual. For example, it is known that the biometric information items which are considered to be capable of being used for authentication include fingerprints, eye retinas and irises, a face, veins, DNA (deoxyribonucleic acid), and so forth.
In recent years, with the development of a biometric authentication technique, there have been provided various types of apparatuses for authenticating an individual by recognizing biometric features of part of a human body. In this biometric authentication, the authentication of an individual is performed by comparing biometric information acquired during registration thereof and biometric information acquired during authentication.
To improve the accuracy of individual authentication using such biometric information, it is desirable to acquire accurate biometric information, and therefore the authentication apparatuses acquire biometric information under sensing conditions made identical. To this end, there has been proposed an authentication apparatus that announces the user (person to be authenticated) that a portion for biometric feature detection of a living body is required to have an appropriate positional relationship with a sensor, to thereby guide the portion for biometric feature detection to a position ensuring the appropriate positional relationship with the sensor (see e.g. Japanese Laid-Open Patent Publication No. 2006-42880).
Further, to provide an efficient guide to conditions under which an image is picked up for registration, there has been proposed an authentication apparatus that displays a photographed image in a manner superimposed on the silhouette of a registered hand (see e.g. Japanese Laid-Open Patent Publication No. 2008-71158).
For example, the authentication apparatus that guides the portion for biometric feature detection to a position having an appropriate positional relationship with the sensor performs a conventional authentication control process, as illustrated in FIG. 15.
The authentication control process 90 acquires an image from the sensor 95, and outputs a result of verification to a user application 97. The authentication control process 90 acquires the image from the sensor 95 by an image acquiring process 91, and passes the acquired image to a position and posture determination process 92. The position and posture determination process 92 determines the position and the posture of a portion for biometric feature detection, and passes a result of determination together with the acquired image to a guide GUI (graphical user interface) display process 93. If the position and posture determination process 92 determines that the position and the posture of the portion for biometric feature detection is not appropriate, the position and posture determination process 92 requests the image acquiring process 91 to acquire an image. The guide GUI display process 93 displays a guide GUI display image 96 on a monitor or the like, to thereby guide the living body portion for biometric feature detection to a position having an appropriate positional relationship with the sensor 95. Further, the position and posture determination process 92 requests a verification process 94 to perform verification, and passes the acquired image to the verification process 94. The verification process 94 verifies the acquired image against an image or a feature of the living body, registered in advance, and outputs a result of the verification.
Further, there has been proposed a technique for assisting in photographing by inversion of the luminance of contour information or display on the monitor by gradation correction (see e.g. Japanese Laid-Open Patent Publication No. 2009-5273).
However, a photographed image displayed for guiding the portion for biometric feature detection to a position having an appropriate positional relationship with the sensor sometimes does not have sufficient visibility for user's recognition, and therefore the photographed image sometimes does not properly function as a guide silhouette unless further processing is executed thereon. Further, when the photographed image is subjected to special processing, for display, the display of the image is delayed from an actual movement, which sometimes hinders the photographed image from properly functioning as a guide silhouette.
Further, when a photographed image including biometric information is displayed, a privacy or security problem sometimes occurs, and hence such a photographed image is sometimes inappropriate as a display image depending on an environment where authentication is performed.